1. Field of the Invention
This invention relates to an assembly for a fluorescent lamp and method for enclosing a fluorescent lamp with a protective cover guard.
2. Discussion of the Art
Fluorescent lamps are used in a wide variety of applications. However, envelopes of the fluorescent lamps are relatively fragile and often subject to breakage, especially in environments where the lamps are exposed to extreme temperatures or stress. Therefore, it is highly advantageous for the lamp to be protected such that the risk of breakage is reduced and the effect of any breakage is mitigated. A protective cover guard enclosing the lamp envelope and fastened to a lamp base attached at the end of the lamp envelope is often used to protect the lamp and to contain glass fragments and powders from escaping into the environment.
A lamp assembly is known in which a protective cover guard encloses a lamp envelope and is attached to a lamp base at each end of the lamp with a collar that is shrink fit over the lamp base and an end portion of the protective cover guard. An adhesive layer is used to bond the collar to the cover guard and the base. However, this is a relatively complex assembly and is expensive to produce.
A lamp assembly is also known in which the protective cover guard is coupled to the lamp base by an adhesive and an overlapping retaining ring. The ring is pre-molded and is chamfered so that it conforms to the chamfer on the lamp base. The applied adhesive secures the cover guard and retaining ring to the lamp base and seals the entire assembly. This assembly is also expensive to produce and labor intensive to manufacture and assemble. In addition, this type of retaining ring increases the overall diameter of the lamp, creating the possibility that the lamp will not fit into conventional lamp outlet structures.
A protective lamp assembly is also known that uses only a cover guard and an adhesive layer to seal and protect the lamp envelope. The cover guard encloses the lamp envelope and extends over the lamp base. A layer of adhesive is placed around the lamp base. The area of the cover guard is heated to shrink fit the cover guard to the adhesive covered base and form a tight seal. Problems in manufacturing may be experienced in this type of assembly however. With no positive exterior force holding the cover guard to the lamp base, the seal between the two may fail, compromising the integrity of the assembly.
Although these and other prior lamp assemblies might provide satisfactory results, they each have certain disadvantages. Many of the previous lamp assemblies result in increased manufacturing and assembly costs. In addition to the cost of the protective cover guard, known lamp assemblies require the use of an adhesive layer to bond the cover guard, the end-cap and/or the ring to the lamp base. The application of the adhesive increases the time and cost required in manufacturing the lamps. Additionally, in many of the existing processes, the cover guard must be manually held in place over the lamp base while the cover guard is heated to shrink fit onto the lamp base. This is labor intensive and slows production. Another disadvantage to many previous protective covers is that the end-cap or ring that fits over an end portion of the cover guard increases the overall diameter of the lamp assembly. As a result, some lamps equipped with these protective covers are too large for conventional fluorescent lamp fixtures. Those lamps without a positive retainer situated exterior to the cover guard may suffer from weak or broken seals.
In an exemplary embodiment, a fluorescent lamp assembly includes a lamp envelope and attached lamp base, a protective cover guard, and a rigid clip or ring.
The cover guard is received over the lamp envelope such that it extends coaxially with the envelope. The cover guard is slightly longer than the glass envelope, and extends slightly over the lamp base at the end of the envelope. A rigid clip of metal or plastic is then placed over the cover guard at a region where the cover guard overlaps the lamp base. The diameter of the clip is smaller than an outer diameter of the cover guard so that the clip exerts a compressive force on the cover guard and lamp base when deployed. In this manner, the cover guard is sealed to the lamp base at the point where the clip is seated.
The cover guard is preferably sealed to the lamp base by heat shrinking the cover guard to the lamp base.
The clip preferably contains a plurality of offsets to facilitate placing the ring over the cover guard with automated machinery.
A second embodiment of the invention uses a molded plastic or stamped metal ring that is received over the lamp base and has an annular cavity to accept the cover guard. The end of the cover guard is inserted into the cavity and secured therein.
One advantage of the present invention is the provision of a lamp assembly that provides protection against the dispersion of glass and internal lamp components in the event of lamp breakage.
Another advantage of the present invention resides in the reduction in labor and expense required to produce a safety lamp assembly.
Another advantage of the present invention is realized by minimizing the outside diameter of the lamp assembly and eliminating the need for an end-cap.
Another advantage of the present invention is the provision of a safety fluorescent lamp assembly having a positive exterior force securing the cover guard to the lamp base.